1. Field of the Invention
This invention relates to a liquid crystal display utilized in a closed-captioned subtitle system for movie theaters. More specifically, this invention relates to a liquid crystal display in which special glasses are utilized by the hearing impaired in order to see the subtitles and movie-goers able to hear, and who do not use the glasses, do not see the subtitles.
2. Description of the Prior Art
Liquid crystal displays are well known and have been used in many applications. A liquid crystal is a state of matter that mixes the properties of both the liquid and solid state. They are catagorized in two ways: (1) Thermotropic liquid crystals, prepared by heating the substance; and (2) Lyotropic liquid crystals, prepared by mixing two or more components, one of which is polar in character. The thermotropic liquid crystals are divided according to structural characteristics into two classes (1) nematic (thread-like) and (2) smectic. In the present invention, cholesteric (twisted) nematic liquid crystals with added chiral compound are sandwiched between two etched transparent glass electrodes. The molecules in the ordinary nematic structure maintain a parallel or nearly parallel arrangement to each other along the molecular axis. They are mobile in three directions and can rotate about one axis. These substances melt sharply at one temperature, but produce a turbid melt. On further heating to a higher temperature, the turbid melt abruptly changes to a clear isotropic liquid which exhibits the same optical properties in all directions. In the temperature range between the solid and the isotropic liquid, these materials are anisotropic, meaning their optical properties vary depending on direction of measurement with respect to the different crystal axes. These crystals are anisotropic with respect to light when viewed between crossed polaroids.
In the cholesteric-nematic structure, the direction of the long axis of the molecule in a given layer is slightly displaced from the direction of the molecular axis of the molecules in an adjacent layer. If a twist is applied to a molecular packing, a helical structure is formed. The helix has a pitch which is temperature-sensitive. The helical structure serves as a diffraction grating for visible light. Chiral compounds show the cholesteric-nematic (twisted-nematic) structure; for example, the cholesteric esters can be used.
If a back lighted nematic liquid crystal is placed between two crossed polarizers to form the liquid crystal display, the light would be polarized by passing through the first polarizer. The polarized light entering the cell would follow the twist of the nematic liquid crystal and would be rotated 90 degrees and, as such, can allow passage of the light through the second polarizer. Application of an electrical field changes the molecular alignment in the liquid crystal such that the polarization is not altered in the cell and no light is transmitted. Thus, an alphanumeric display can be formed by proper application of an electric field to form regions of polarized and cross-polarized light within the display.
All liquid crystals are fabricated in a similar fashion. A thin film of liquid crystal approximately .0005 inches thick is sandwiched between two glass plates. Electrodes are coated on the inside of the glass plates. The electrical equivalent circuit of this assembly is a capacitor with the liquid crystal as the dielectric. As indicated above, the preferred liquid crystal used in the present invention is a nematic crystal which, depending on temperature, exhibits both isotropic and anisotropic physical properties. The fabrication of liquid crystal displays is well known and will not be described in any detail here (see U.S. Pat. No. 3,322,485 to R. Williams). In addition, there are many methods of driving a liquid crystal display to produce the desired alphanumeric subtitle display and these driving systems will not be discussed in great detail herein.
It has been well known to provide subtitles on movies, particularly those in a foreign language, and methods to provide such subtitles are disclosed in U.S. Pat. No. 4,673,266 issued to Fiumi which discloses a method and apparatus for displaying subtitles which utilizes a microprocessor decoder system to detect and decode information contained on a standard movie film print. The microprocessor forms subtitles on suitable displays which are constantly viewable by those in the audience.
U.S. Pat. No. 4,647,966 to Phillips et al discloses a stereoscopic three-dimensional large-screen liquid crystal display which may be viewed stereoscopically using polarized glasses with appropriately oriented polarizing axes. This device uses liquid crystal light valves to produce images which are controlled, in real time, by computer image generation. U.S. Pat. 4,613,207 to Fergason discloses a liquid crystal image forming projector in which the light from the liquid crystal display is selectively scattered or transmitted by respective portions of the display. The patent teaches that a polarizer can be used to aid in this image production.
There has been a long felt need by the hearing impaired to be able to view movies in movie theaters with a subtitling system similar to that used on closed-captioned television programs. It would be especially helpful to provide a subtitle system for movie viewing in which only the hearing impaired would see the subtitles while the non-hearing impaired would listen to the dialogue without the distraction of subtitles on the screen. It can be seen that this would allow a family having one hearing-impaired individual to attend a movie viewing as a group with the hearing-impaired individual selectively being able to view the subtitles while his non-hearing-impaired relatives could listen to the dialogue in the usual fashion.
The subtitle system of the present invention provides a solution to this long-felt problem by providing a liquid crystal display under or at the lower portion of a standard movie screen which display utilizes only one polarizer in the optical system of the liquid crystal display. Thus, light transmitted through or reflected from the display can only be viewed by an individual wearing lenses which are polarized 90 degrees either to the single polarizer used in the liquid display optical system or to the image produced by the display. Normally, the cross-polarized lens would be mounted in special glasses either provided by the movie theater management or being the personal property of the hearing impaired individual for use in movie theaters or other situations where selective image viewing for the hearing impaired is provided in accordance with the concept of the present invention.
It can be seen that by utilizing the liquid crystal display in which polarized light is produced, only those viewing the motion picture through a polarized lens crossed with respect to the optical system of the liquid crystal display would be able to view the subtitles generated and, therefore, the hearing segment of the viewing audience would be totally unaware of the captioning. The system of the present invention satisfies a long-felt need among the hearing impaired and will enable them to attend viewings in a movie theater with their hearing relatives and friends. Those wearing the polarized lenses would still see the non-polarized light reflected from the movie screen, albeit at a slightly reduced intensity.
It can also be seen that the subtitle system of the present invention can be used to selectively provide subtitles for films such as when a film is shown in an area with a population speaking two different languages, for instance, an English dialogue film shown with Spanish subtitles selectively viewable by those members of the audience who do not understand spoken English but who can read Spanish. Additionally, an English dialogue film shown in a country where English is widely spoken as a second language and which film may not be "dubbed" into the dominant language in that country, can have native language subtitles selectively displayed for those who are unable to understand the English dialogue.